Generally, when blowout, run out of fuel and the like occurs because of a malfunction of components configuring an internal combustion engine, such as an injector, a fuel pump, an ignition coil, an ignition plug and the like, a deterioration in drivability, a malfunction of a control system and the like, a decrease of number of rotations (i.e. rotational speed) of the internal combustion engine exceeding a control range thereof, in other words, a recoverable decrease of the number of rotations of the internal combustion engine (i.e. an engine stall) may be caused. Furthermore, when a driver suddenly and deeply depresses a brake pedal while a vehicle travels on a low friction road, tires may slip, which may cause a lock of the tires. As a result, the number of rotations of the internal combustion engine may rapidly decrease, which may further result in causing the engine stall.
A valve timing control apparatus disclosed in JP2002-256912A is configured so as to execute a control in view of an engine stall. The valve timing control apparatus disclosed in JP2002-256912A includes a first detecting means, a second detecting means and a determining means. The first detecting means detects a deviation between an actual number of rotations (i.e. an actual engine speed) of an internal combustion engine and a reference number of rotations (i.e. a reference engine speed) of the internal combustion engine. The second detecting means detects a changing rate of the actual number of rotations of the internal combustion engine (i.e. changes in the actual number of rotations of the internal combustion engine). The determining means determines a chance of the engine stall of the internal combustion engine to happen on the basis of detection results of the first and second detecting means. Then, the valve timing control apparatus disclosed in JP2002-256912A is controlled on the basis of a determination result of the determining means.
The valve timing control apparatus disclosed in JP2002-256912A further includes a lock mechanism, which corresponds to first and second lock portions, for locking a relative rotational phase at a predetermined phase (i.e. an intermediate phase) between a most retarded angle phase and a most advanced angle phase. The predetermined phase is set as a phase corresponding to an opening/closing timing of an intake valve by which a startability of the internal combustion engine is improved.
The determining means determines that “the engine stall is unavoidable” in a case where a decrease of the number of rotations of the internal combustion engine is rapid. On the other hand, in a case where the decrease of the number of rotations of the internal combustion engine is small or in a case where the decrease of the number of rotations of the internal combustion engine is not detected, the determining means determines that “the engine stall is not likely to occur”. Furthermore, in a case where the determining means determines that the engine stall is avoidable even if the decrease of the number of rotations of the internal combustion engine is detected, the determining means concludes that “the engine stall is avoidable”.
Then, in the case where the determining means determines that the “engine stall is not likely to occur”, more specifically, in a case where a determination index such as the deviation of the number of rotations and the like falls within a first area, a normal control is executed to the valve timing control apparatus. In the case where the determining means determines that “the engine stall is avoidable”, more specifically, in a case where the determination index such as the deviation of the number of rotations and the like falls within a second area, the relative rotational phase established by the valve timing control apparatus provided at the intake valve is shifted to a retarded angle phase relative to the predetermined phase in order to reduce an overlap between a valve opening timing of the intake valve and a valve opening timing of an exhaust valve, or in order to eliminate the overlap between the valve opening timing of the intake valve and the valve opening timing of the exhaust valve. Accordingly, combustibility of the internal combustion engine may be increased, which may result in avoiding the engine stall. Still further, in the case where the determining means determines that “the engine stall is unavoidable”, more specifically, in a case where the determination index such as the deviation of the number of rotations and the like falls within a third area, the relative rotational phase is set as the predetermined phase in order to prepare for an appropriate restart of the internal combustion engine.
In sum, the valve timing control apparatus disclosed in JP2002-256912A executes different controls of the relative rotational phase depending on the number of rotations of the internal combustion engine in order to avoid the engine stall or in order to prepare for the appropriate restart of the internal combustion engine after the engine stall occurs.
There exists a valve timing control apparatus of an intake valve, which is configured so that a phase area is set at a predetermined range from a most retarded angle phase to an advanced angle phase so that an internal combustion engine is not startable, in other words, an area of the Atkinson cycle (which will be hereinafter referred to as an Atkinson area) is set in a predetermined range from the most retarded angle phase to the advanced angle phase. In a case where a driving state of the internal combustion engine is in a middle-to-low load area where a throttle opening degree is small, e.g. in a case where the internal combustion engine is in an idle state and the like, a relative rotational phase is set so as to fall within the Atkinson area. According to the known valve timing control apparatus including the Atkinson area, an explosive expanding operation becomes greater than a compression operation, so that a relatively great work may be obtained with a relatively small amount of air and fuel. As a result, a pumping loss may be reduced, so that fuel consumption is improved.
However, because the valve timing control apparatus disclosed in JP2002-256912A is configured so as to determine the chance of the engine stall to happen on the basis of the decrease of the number of rotations of the internal combustion engine, in other words, because the valve timing control apparatus disclosed in JP2002-256912A is configured so as to execute a phase control when the number of rotations of the internal combustion engine starts decreasing, a discharge pressure of a pump is already decreased at a point of time specifically when the determining means determines that “the engine stall is unavoidable”, so that the relative rotational phase may not be shifted to the predetermined phase. As a result, for example, the internal combustion engine may be stopped while the relative rotational phase forms a phase closer to the advanced angle phase relative to the predetermined phase.
Furthermore, the determining means is configured so as to determine that the “the engine stall is unavoidable” in the case where the determination index of the deviation of the number of rotations of the internal combustion engine and the like falls within the third area. The second area is set between the first area, within which the determination index is found while the vehicle is normally driven, and the third area. Therefore, in the case where the rapid decrease of the number of rotations of the internal combustion engine occurs while the relative rotational phase establishes the phase closer to the retarded angle phase relative to the predetermined phase, a retarded angle control is once executed while the determination index is within the second area, although an advanced angle control needs to be executed in order to shift the relative rotational phase to correspond to the predetermined phase. Therefore, an advanced angle control amount to be applied while the determination index is within the third area becomes great, so that the relative rotational phase may not be shifted towards the predetermined phase. As a result, the internal combustion engine may be stopped while the relative rotational phase establishes the phase closer to the retarded angle phase relative to the predetermined phase.
The valve timing control apparatus disclosed in JP2002-256912A does not use the Atkinson are, therefore, even if the internal combustion engine is stopped while the relative rotational phase establishes the phase closer to the retarded angle phase relative to the predetermined phase, the internal combustion engine may be restarted. However, according to the known valve timing control apparatus using the Atkinson area, the internal combustion engine may not be appropriately restarted while the relative rotational phase establishes the phase closer to the retarded angle phase relative to the predetermined phase.
A need thus exists for a valve timing control apparatus which is not susceptible to the drawback mentioned above.